U.S. Frost Dates by Weather Station

NOAA station USC00218419 · Minnesota

Frost Dates for Two Harbors, MN

NOAA weather station Two Harbors (USC00218419), Minnesota · elevation 625 ft (191 m) · hardiness zone 4b*

  • Lower-risk planting dateafter May 30only 1 spring in 10 still has a frost later
  • Typical last frostMay 1250% chance of a frost after it
  • Typical first fall frostOctober 650% chance of a frost before it
  • Frost-free season145 daystypical year, 32°F
  • Hardiness zone4bcalculated*

The year at a glance

Frost season at Two Harbors, MNSpring: a frost after April 30 in 9 years out of 10, after May 12 in half of the years, after May 30 in 1 year out of 10. Fall: the first frost comes before September 19 in 1 year out of 10, before October 6 in half of the years, before October 21 in 9 years out of 10. Typical frost-free season: 145 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 12First frost ~Oct 6Frost season at Two Harbors, MNSpring: a frost after April 30 in 9 years out of 10, after May 12 in half of the years, after May 30 in 1 year out of 10. Fall: the first frost comes before September 19 in 1 year out of 10, before October 6 in half of the years, before October 21 in 9 years out of 10. Typical frost-free season: 145 days.JFMAMJJASONDLast frost ~May 12First frost ~Oct 6
frost likely chance fading 90% → 10% frost-free in a typical yearThe year at a glance. Blue: frost is likely; the gradient fades as the chance drops from 90% to 10%; green: the frost-free part of a typical year.

Frost dates (32°F)

Probability of frost, based on 30 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 30September 19
50% (typical)May 12October 6
90% (likely)April 30October 21
Frost-free season (32°F, 50% chance)
145 days
Hard frost (28°F), last in spring, 50% chance after
April 29
Hard frost (28°F), first in fall, 50% chance before
October 20

The last 15 years (2006–2020 normals)

Typical last frost May 13 (1 day later than the 30-year normal), typical first fall frost October 9 (3 days later). Frost-free season 148 days.

A shorter, more recent NOAA period. The 30-year normals above remain the main reference: 15 years carry more year-to-year noise.

Add these dates to your calendar Yearly reminders for the typical last frost, the lower-risk planting date and the typical first fall frost (.ics).

How the chance of frost changes with the date

Spring at Two Harbors: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 30, 20% May 24, 30% May 19, 40% May 15, 50% May 12, 60% May 9, 70% May 6, 80% May 3, 90% April 30. Observed last spring frost in recent years: 2021 May 29, 2022 May 5, 2023 May 3, 2025 May 10, 2026 May 11.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 30May 12Apr 302021: May 292022: May 52023: May 32025: May 102026: May 11Fall at Two Harbors: chance of a frost before this dateFall, chance of a frost before the date: 10% September 19, 20% September 26, 30% September 30, 40% October 3, 50% October 6, 60% October 9, 70% October 12, 80% October 17, 90% October 21. Observed first fall frost in recent years: 2021 October 22, 2023 October 28, 2025 October 24.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 19Oct 6Oct 212021: October 222023: October 282025: October 24
Two charts, because spring and fall answer different questions: in spring, the chance that a frost still comes after a date; in fall, the chance that the first frost has already come before it. NOAA publishes these odds from 10% to 90%, so the lines stop there. ◆ marks the actual date in each recent year.

What actually happened in recent years

Observed dates of the last spring and first fall frost (32°F) at this station; ◆ marks them on the charts above
YearLast spring frostFirst fall frost
2021May 29October 22
2022May 5incomplete record
2023May 3October 28
2024incomplete recordno data
2025May 10October 24
2026May 11season not over yet

What these dates mean

Setting out tender crops on the early spring date, April 30, carries a 90% chance of a light frost and is a gamble in Two Harbors. A more cautious approach waits until May 30, when only a 10% chance of a light frost remains. In the fall, the cautious date to finish harvesting tender crops is September 19, which also has a 10% chance of a light frost, while waiting until October 21 would be a gamble with a 90% chance.

The 50% spring date, May 12, indicates a 50% chance of a light frost later than this date, and the 50% fall date, October 6, indicates a 50% chance of a light frost earlier than this date. The hard-frost median dates are April 29 in spring and October 20 in fall; a hard frost at 28 °F can damage plant tissue that survives a light frost at 32 °F. The record spans 30 years and the interval between the two 32 °F 50% dates is 145 days.

How to read the probabilities

The dates are probabilities from 30 years of weather, not a forecast for this year.

  • Spring: "10% after May 30" means that in about one spring out of ten a frost still happens after that date. The 90% date is the earliest: a frost after it happens in most years.
  • Fall: "10% before September 19" means that in about one fall out of ten the first frost arrives before that date.
  • 50% is the typical date: half of the years are earlier, half are later.
  • A light frost (32°F) damages tender plants; a hard frost (28°F) also stops most hardy vegetables.

Nearby weather stations

Map of weather stations near Two Harbors, MNNumbered nearest stations: 1 — Superior, WI — 28 mi; 2 — Wolf Ridge Elc, MN — 36 mi; 3 — Madeline Island, WI — 46 mi; 4 — Cloquet, MN — 46 mi; 5 — Eveleth, MN — 50 mi.MNWI25 mi · 40 km1. Superior, WI — 28 mi12. Wolf Ridge Elc, MN — 36 mi23. Madeline Island, WI — 46 mi34. Cloquet, MN — 46 mi45. Eveleth, MN — 50 mi5
  1. Superior, WI 28 mi (45 km)
  2. Wolf Ridge Elc, MN 36 mi (58 km)
  3. Madeline Island, WI 46 mi (74 km)
  4. Cloquet, MN 46 mi (74 km)
  5. Eveleth, MN 50 mi (81 km)

Sources

* Hardiness zone 4b: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 47.0258, -91.6653.